Flanges are critical components used in piping systems to connect pipes, valves, pumps, and other equipment. They provide easy access for cleaning, inspection, or modification. Flanges come in various types, each designed for specific applications, pressures, temperatures, and materials. Below is a detailed overview of the different types of flanges:

1. Based on Face Type

The face of a flange determines how it seals with the gasket and mating flange. Common face types include:

a. Flat Face (FF)

• The sealing surface is flat and level.

• Used for low-pressure applications.

• Typically paired with flat gaskets.

• Common in cast iron and ductile iron systems.

b. Raised Face (RF)

• The sealing surface is raised above the bolting circle.

• Provides a higher pressure seal compared to flat face flanges.

• Commonly used in industrial applications.

• The raised face helps concentrate pressure on the gasket.

c. Ring-Type Joint (RTJ)

• Features a groove for a metal ring gasket.

• Used in high-pressure and high-temperature applications (e.g., oil and gas).

• Provides a tight, leak-proof seal.

d. Tongue and Groove (T&G)

• Consists of a tongue on one flange and a matching groove on the other.

• Ensures precise alignment and a tight seal.

• Used in high-pressure systems.

e. Male and Female (M&F)

• The male face has a raised area, while the female face has a recess.

• Provides better gasket alignment and sealing.

• Suitable for moderate pressure applications.

2. Based on Connection Type

Flanges are categorized based on how they connect to the piping system:

a. Weld Neck Flange (WN)

• Features a long tapered hub that is welded to the pipe.

• Provides excellent strength and stress distribution.

• Ideal for high-pressure and high-temperature applications.

b. Slip-On Flange (SO)

• Slides over the pipe and is welded on both the inside and outside.

• Easier to install than weld neck flanges.

• Suitable for low-pressure applications.

c. Socket Weld Flange (SW)

• The pipe is inserted into the socket and welded around the top.

• Provides good flow characteristics and strength.

• Used for small-diameter, high-pressure pipes.

d. Threaded Flange

• Connects to the pipe using threads (no welding required).

• Ideal for low-pressure, non-critical applications.

• Commonly used in piping systems where welding is not feasible.

e. Lap Joint Flange

• Used with a stub end, which is welded to the pipe.

• The flange rotates around the stub end, allowing for easy alignment.

• Suitable for systems requiring frequent disassembly.

f. Blind Flange

• A solid flange used to close the end of a pipe or valve.

• Provides easy access for inspection or cleaning.

• Commonly used in pressure testing applications.

3. Based on Pressure-Temperature Ratings

Flanges are designed to withstand specific pressure and temperature conditions. Common standards include:

• ASME B16.5: Covers flanges up to 24 inches in diameter.

• ASME B16.47: Covers larger flanges (26 inches and above).

• PN Ratings: European pressure rating system (e.g., PN10, PN16).

4. Based on Material

Flanges are made from various materials depending on the application:

a. Carbon Steel

• Commonly used in industrial applications.

• Suitable for moderate temperatures and pressures.

b. Stainless Steel

• Resistant to corrosion and high temperatures.

• Used in chemical, food, and pharmaceutical industries.

c. Alloy Steel

• Contains additional elements like chromium, molybdenum, or nickel.

• Used in high-temperature and high-pressure applications.

d. Ductile Iron

• Stronger and more durable than cast iron.

• Used in water and wastewater systems.

e. PVC and Plastic

• Lightweight and corrosion-resistant.

• Used in low-pressure, non-critical applications.

5. Specialized Flanges

Some flanges are designed for specific applications:

a. Orifice Flange

• Used to measure the flow rate of liquids or gases.

• Features a small hole (orifice) for flow measurement.

b. Expander Flange

• Increases the pipe size from a specific point.

• Used to connect pipes of different diameters.

c. Reducing Flange

• Connects pipes of different sizes.

• Combines the functions of a flange and a reducer.

d. Spectacle Blind Flange

• Consists of two metal discs (one solid, one with a hole).

• Used to isolate sections of a pipeline.

e. Long Neck Welding Flange

• Similar to a weld neck flange but with a longer neck.

• Used in high-pressure and high-temperature applications.

6. Standards and Specifications

Flanges are manufactured according to international standards to ensure compatibility and safety:

• ASME/ANSI: American standards for flanges.

• DIN: German standards.

• EN: European standards.

• JIS: Japanese standards.

• BS: British standards.

7. Flange Dimensions

Flange dimensions are standardized and include:

• Outside diameter (OD)

• Bolt circle diameter (BCD)

• Number of bolt holes

• Bolt hole diameter

• Thickness

8. Gaskets and Bolting

Flanges require gaskets and bolts to create a seal:

• Gaskets: Made from materials like rubber, PTFE, or metal.

• Bolts: Must match the flange material and pressure rating.

9. Applications

Flanges are used in various industries, including:

• Oil and gas

• Chemical processing

• Water treatment

• Power generation

• HVAC systems

Thank you.